Fix read of uninitialised variables in embed_sim_init
Fix read of uninitialised variables in embed_sim_init

If get_module_ref fails (e.g. because it can't find the cocotb module) then cocotb_module and arg_dict may contain garbage values after the jump to cleanup which potentially calls Py_DECREF on them.

stuarthodgson/cocotb,mkreider/cocotb2,stuarthodgson/cocotb,mkreider/cocotb2,stuarthodgson/cocotb,mkreider/cocotb2